The invention relates to use of optical circuitry to detect liquid level by sensing whether an optical component of the circuitry is or is not currently immersed in the liquid. More particularly, the invention is concerned with the nature and structure of the involved optical component.
Prior and present liquid-level sensing and measurement have relied on magnetic-reed switch technology, wherein a float carries one or more magnets to create a magnetic field which rises and falls with liquid level, and one or more reed switches at fixed elevations along the path of float movement respond to proximity of the magnetic field as the float tracks instantaneous liquid level, by providing on/off switch action in an electrical circuit.
Pending U.S. patent application Ser. No. 146,196, filed Jan. 28, 1988 discloses generally similar magnetic-reed constructions wherein an optical circuit is either continuous, or partially or completely broken, depending upon the actuated or unactuated condition of the magnetic-reed structure.
The foregoing devices involve moving parts and are therefore subject to a degree of degraded performance in the presence of any vibration in their environment, and even though the magnetic-reed switch may be hermetically sealed, it must still function with associated electrical conductors, connections and components, thus presenting a potential hazard in the circumstance of monitoring the level of stored inflammable liquids as in a tanker for petroleum products.